A die assembly can be modular and, in any event, is typically assembled from a plurality of parts and then set in a die station as an integral device. For example, a die assembly can comprise a first die part and a second die part, which together form the components that allow the fluid to enter the assembly and be properly emitted therefrom. The first die part includes a first lip and the second die part includes a second lip, these lips defining a feed gap therebetween that determines the thickness of the fluid film emitted therefrom.
A die assembly can have a fixed feed gap or a flexible feed gap. With a fixed feed gap, the lips are not movable relative to each other, whereby the thickness of the feed gap will always be of the same known dimension. With a flexible feed gap, one lip is movable relative to the other lip so as to enable the adjustment of the feed gap along the width of the assembly. A flexible feed gap is typically accomplished by assembling the first die part so that it contains a flexible web between its rear portion and its front portion (to which the first lip is attached), as well as means for moving the front portion in localized areas. Movement of the front portion results in the adjustment of the position of the lip relative to the other lip and, thus, the thickness of the feed gap in the relevant localized area.
In flexible feed gap operations, localized adjustments of the feed gap can usually be accomplished with conventional die assembly designs in order to accommodate a particular run. However, once initial adjustments are made (i.e., once the movable lip is moved from its original adjustment), returning the lip to a known position is not so easily done, if it is even possible. Also, without a clean die and specialized equipment, it is impossible to adjust a feed gap on an industry standard flex die to a known precision gap opening.